This invention relates to alfalfa, and more particularly to alfalfa products and a method of synthesizing or hybridizing alfalfa products having improved uniformity of selected traits.
Plants, and food plants in particular, such as alfalfa play an important role in everyday life. Alfalfa, genus Medicago Sativa, perhaps the most important forage crop species in the world, provides one of the most effective sources of biological nitrogen fixation. While being an extremely energy-efficient food source, alfalfa also provides an excellent source of vitamins and minerals. Alfalfa improves soil tilth making it ideal for crop-rotation. Crop-rotation replenishes nutrients in soil depleted from other crops, such as corn.
The area of alfalfa cut for hay in the United States exceeds 25 million acres. Commercial alfalfa seed may be provided either in a synthetic variety or a hybrid variety. The prior art commercial production of alfalfa seed involves multiple stages. For synthetic varieties the stages may include a breeder seed production stage, a foundation seed production stage, a register seed production stage and a certified seed production stage. Hybrid variety seed production may involve up to three stages including a breeder seed production stage, a foundation seed production stage and a certified seed production stage.
Breeder seed is an initial increase of seed produced from the strains or clones that are developed by a breeder. Foundation seed is a second generation increase of seed produced from the breeder seed. Register seed may be derived from foundation seed. Certified seed may be derived from breeder seed, foundation seed or register seed. Breeder seed descends from a selection of recorded origin, under the direct control of the breeder, a delegated representative or a state or federal inspection service, such as the AOSCA (Association of Official Seed Certification Analysts) in the U.S.A. Certified seed is used in commercial crop production. Certified seed is usually grown, processed and labeled under supervision and-regulation of a public agency.
Efforts in developing healthy and productive alfalfa varieties often focus on breeding for disease and stress-resistant cultivars, for example, breeding for persistence, breeding for adaptation to specific environments, breeding for yield per se, and breeding for quality. Success has been attained in breeding for resistance to such diseases as bacterial wilt, see, e.g., Elgin, Jr., et al., xe2x80x9cBreeding for Disease and Nematode Resistance,xe2x80x9d Alfalfa and Alfalfa Improvement (ed. by Hanson, A. A., et al. 1988), pp. 830-832; anthracnose, id. at 832-833; and common leaf spot, id. at 835-836. Breeders have had less success in breeding for yield and quality per se, although methods have been developed that help increase productivity and yield, see, for example, U.S. Pat. No. 4,045,912 to Sun, incorporated herein by reference. Historically, yield and productivity, quality and persistence are objectives of high concern to farmers.
In the area of breeding for adaptation to specific climates, breeders have developed winterhardy varieties of alfalfa for growing in colder climates. In general, breeders developed winterhardy varieties by using an average fall dormancy score or fall growth score as a predictor. Average fall dormancy scores are made on a scale of one to nine, with a score of nine reflecting the highest fall growth and a score of one reflecting the lowest fall growth. A correlation coefficient as high as 0.95 has been reported between average fall dormancy score and winter injury score. See Barnes, D. K., et al., xe2x80x9cFall Dormancy Score in Alfalfa: A Valuable Predictive Tool,xe2x80x9d Report of the 26th Alfalfa Improvement Conference, Brookings, S. D. (ed. by Barnes, D. K. Jun. 6-8, 1978), p. 34. However, even in winterhardy varieties of alfalfa, there is significant variation and lack of uniformity among individual alfalfa plants in their degree of winterhardiness; thereby decreasing the potential productivity of these varieties.
A number of other factors also limit the yield and quality of alfalfa fields. In particular, the lack of uniformity in development rate, sometimes measured by flowering dates, is one factor that can cause yield from alfalfa fields to be less than optimal. The highest growth rate for yield and quality of individual alfalfa plants occurs from the early bud to the late bud stage. The date this stage occurs in individual plants varies widely. As a practical matter, however, the harvester of a field of alfalfa must harvest the entire field at one time. As a consequence, when a field of alfalfa plants lacks uniformity in flowering dates or maturity, a high proportion of harvested plants have reduced yield and nutrient value, either because they are too old or too young.
Like flowering dates, another factor that limits the yield of an alfalfa plant may be the lack of uniformity in flowering frequency. Individual alfalfa plants may flower once, twice, three times, ten times or more over the course of a year. Generally, the higher the flowering frequency, the faster the alfalfa plant develops, and the lower the flowering frequency, the slower the alfalfa plant develops. Flower frequency and flowering date vary widely in a population of alfalfa plants. For maximum yield and quality of alfalfa, the producer""s harvest frequency should be synchronized with the flowering frequency.
Lack of uniformity in fall dormancy also has reduced the yield and quality of alfalfa fields in both colder and warmer climates. Varieties having uniformity and shorter fall dormancy in either warmer or colder climates may increase the length of the growing season and reduce dormancy time. Consequently, both yield and quality may be increased.
To date, most alfalfa breeding programs emphasize maximizing the heterogeneity of a given alfalfa variety in order to improve yield and stability. This approach, however, results in wide variation in many characteristics, such as flowering dates, flower frequency, development rate, growth rate, fall dormancy and winterhardiness. Prior art breeding methods do not emphasize improving the uniformity of these characteristics. Rather, prior art breeding methods emphasize selection of good germplasm for specific purposes, such as disease resistance, regardless of uniformity for other characteristics.
Prior art methods do not perform selection for desired traits after the stage of increasing seed. Prior art methods also do not include selection of individual plants for the traits of flowering dates, flower frequency, development rate, growth rate and fall dormancy. Furthermore, prior art breeding methods have not included subsequent classification stages of individual plants for these traits.
It is therefore a motivation of the invention to provide alfalfa and an alfalfa product and a process for synthesizing alfalfa and an alfalfa product that improves uniformity of selected traits.
The invention provides alfalfa and an alfalfa product having improved uniformity of one or more selected traits including flowering dates, flower frequency, development rate, growth rate, fall dormancy and winterhardiness. The alfalfa product may also provide improved predictability of these traits. By using two or more of the invented alfalfa products having different mean flowering dates, a scheduled harvest system may be established. The scheduled harvest system may be designed to allow harvesting of alfalfa varieties at maximum relative feeding value. The invention also includes a method for synthesizing an alfalfa product having increased uniformity for preselected traits.
Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from the detailed description.